Characterization of Key Odor-Active Off-Flavor Compounds in Aged Pasteurized Yogurt by Sensory-Directed Flavor Analysis

Abstract

The purpose of this study was to determine the key odor-active compounds contributing to the off-flavor of aged pasteurized yogurt (APY) using sensory-directed flavor analysis. Additionally, different extraction methods were compared to determine their effects on the volatile compounds, including dynamic headspace sampling (DHS), solid-phase microextraction, and stir bar sorptive extraction, and DHS was found to be suitable for this study. The results showed that comprehensive twodimensional gas chromatography−olfactometry−mass spectrometry analysis (GC × GC−O−MS) had more advantages in separating and identifying the volatile compounds than the traditional GC−O−MS. A total of 17 odor-active compounds were determined in the fresh pasteurized yogurt and APY samples by DHS coupled with GC × GC−O−MS. The dynamic headspace dilution analysis demonstrated that 2-heptanone and hexanal were the most vital components in APY with the highest flavor dilution factor. Furthermore, the spiking and omission experimental results revealed that the odor-active compounds, such as 2-heptanone, butanoic acid, pentanoic acid, hexanal, and (E)-2-heptenal, were the key odor-active off-flavor contributors in APY. Therefore, these compounds could be used as potential indicators to determine the freshness of pasteurized yogurt.

Variation of Aroma Components of Pasteurized Yogurt with Different Process Combination before and after Aging by DHS/GC-O-MS

“…Milk powder and milk often occur fat oxidation and produce off-odor [ 12 , 13 ]. Although the odor-active off-flavor compounds in aged, pasteurized yogurt have been identified in our previous studies [ 14 ], there are still some shortcomings. The previous research results were only discussed and studied based on a group of samples, and it is unclear how the research results would change when the sample range was expanded.…”

Identification of key aroma‐active compounds in long shelf‐life yoghurt and milk produced by different pre‐sterilisation processes of raw milk using SBSE‐GC × GC–O–MS

“…According to the method (Zhao et al ., 2022) with appropriate modifications. Accurately weighed 10 g of samples (milk or long shelf‐life yoghurt) and 2 g of NaCl were placed in a 40‐mL headspace vial.…”

“…The OAV was calculated as the ratio of the concentration of a compound to its odour threshold. Additionally, the thresholds for different compounds were referenced from literature (Tian et al ., 2019; Wang et al ., 2020a, 2021; Zhao et al ., 2022; Guo et al ., 2023; Yu et al ., 2023, 2024).…”

“…Furthermore, it has high sensitivity and strong separation ability and provides information on all components of samples, especially suitable for separating complex components and trace samples. Currently, this technology has successfully characterised watermelon juice (Yang et al ., 2021), human milk and infant formula (Zhang et al ., 2022) and off‐flavours in pasteurised yoghurt (Zhao et al ., 2022).…”

Sensomics-Assisted Characterization of Fungal-Flowery Aroma Components in Fermented Tea Using Eurotium cristatum

“…Quantification of Volatiles in Tea Infusion. The quantification of aroma-active compounds based on the results of GC−MS/O was performed according to the method of Zhao et al 17 Standards were dissolved in absolute ethyl alcohol and then diluted to eight different concentrations. The prepared standard solutions were placed in liquid phase vials and automatically inserted into the GC−MS inlet using the splitless mode.…”